CREATE DOMAIN DM_GUID AS CHAR(16) CHARACTER SET OCTETS COLLATE OCTETS;

CREATE TABLE GUIDS (
    ID      INTEGER NOT NULL,
    GUID    DM_GUID NOT NULL
);

CREATE PACKAGE PKG_TEST
AS
BEGIN
  FUNCTION TEST(
    in_guid DM_GUID    -- OK
  ) RETURNS guids.ID;  -- Error
END